Design of a Hexad-Polarization Antenna With High Isolation and Switchable Feed Network

Abstract

This article presents a multi-layer hexad-polarization compatible reconfigurable square shaped patch antenna. With an intent to use in the sub–6 GHz spectrum, the proposed antenna’s polarization can be switched among horizontal linear polarization (LP), vertical LP, slant ±45° LP, right-hand circular polarization (RHCP), and left-hand CP (LHCP) by controlling PIN diodes in switchable feed network. By incorporating two orthogonal aperture-coupled switchable feed networks and a 180° phase shifter, the proposed antenna can operate at single or dual feeding mode. The horizontal and vertical LP can be attained by exciting single port. On the other hand, slant +45° LP, –45° LP, RHCP, and LHCP can be achieved by switchable dual port excitation. Low cross-polarization and high isolation in each mode make the proposed antenna more attractive for wireless applications. The proposed antenna has 10-dB impedance bandwidth of 1.19% for LP, 0.89% for LHCP, and 1.19% for RHCP. Moreover, 3-dB axial ratio (AR) bandwidth of 5.97% for RHCP and 7.19% for LHCP are attained. Better isolation characteristic (<-25 dB) is achieved at resonance frequency of 3.34 GHz without utilizing any isolation improvement techniques. The maximum gains of two CP modes and the LP mode are 6.8 dBic, 6.2 dBic, and 6.45 dBi, respectively.